Revealed: the teenage brain upgrades that occur before adulthood

The final brain edit before adulthood has been observed for the first time. MRI scans of 300 adolescents and young adults have shown how the teenage brain upgrades itself to become quicker – but that errors in this process may lead to schizophrenia in later life.

The editing process that takes place in teen years seems to select the brain’s best connections and networks, says Kirstie Whitaker at the University of Cambridge. “The result is a brain that’s sleeker and more efficient.”

When Whitaker and her team scanned brains from people between the ages of 14 and 24, they found that two major changes take place in the outer layer of the brain – the cortex – at this time. As adolescence progresses, this layer of grey matter gets thinner – probably because unwanted or unused connections between neurons – called synapses – are pruned back.

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At the same time, important neurons are upgraded. The parts of these cells that carry signals down towards synapses are given a sheath that helps them transmit signals more quickly – a process called myelination.

Schizophrenia link

“It may be that pruning and myelination are part of the maturation of the brain,” says Steven McCarroll at Harvard Medical School. “Pruning involves removing the connections that are not used, and myelination takes the ones that are left and makes them faster,” he says.

McCarroll describes this as a trade-off – by pruning connections, we lose some flexibility in the brain, but the proficiency of signal transmission improves.

The most profound editing appears to occur in the busiest hubs of the brain, in areas that link various regions together. When Whitaker’s team compared the most edited areas with maps of brain gene activity, they found that the most active genes in these hubs are linked to improving signal speed.

“If you are distressed as a child, you myelinate more quickly, in a kind of panic, instead of taking longer to figure out the optimal processing network,” says Whitaker.

The team is planning to continue re-scanning the brains of the 300 participants in the study, to see if any go on to develop conditions that can be traced back to their teenage brain development. “Not many will develop schizophrenia, but we’re also interest in mood disorders and depression,” says Whitaker.